1. Field of the Invention
The present invention relates generally to a flush-mountable slam-type lock having a spring projected sliding bolt, a handle for retracting the bolt, and a key control for selectively permitting and preventing the handle to move out of a nested position. More particularly, the invention relates to locks of this sort including an automatic one-trip latching linkage of the type which requires that a key control be operated prior to but not necessarily concomitantly with each movement of the handle out of its unlocked position.
While the present invention has particularly advantageous use in conjunction with flush-type door locks used on swinging doors of trucks, industrial cabinets and the like, principles of the invention are not limited in application to such uses.
2. Prior Art
Flush-type door locks including a housing, a slidable lock bolt, and an operating handle for moving the bolt relative to the housing are well known. Usually the handle is in a flush or nested position when the bolt is projected and pivots to an operating position to effect bolt retraction. Locks of this type are well suited for use on swinging doors of vehicles such as trucks, on merchandise, tool and equipment cabinets, and the like.
Flush-type paddle-handle door locks employing a key-turned, rotatable cam for selectively permitting and preventing unlocking movement of a handle, and having a spring projected sliding bolt, are described in U.S. Pat. Nos. 3,707,862 and 3,668,907 granted Jan. 2, 1973 and June 13, 1972, respectively, to John V. Pastva, Jr. Both of these patents disclose the use of a pushrod between a bolt-actuator and a rotatable locking member. An ornamental appearance employed in locks of this general type is illustrated in design U.S. Pat. No. 230,132 issued Jan. 29, 1974 to John V. Pastva, Jr.
In applicant's U.S. Pat. No. 3,209,564, issued Oct. 5, 1965, a flush-type lock construction is described wherein a one-trip unlatching movement of a handle is permitted after a key has been turned once in a lock cylinder. In the described lock construction, a relatively complex mechanism including a separate, spring-biased, detent-controlled slide pin is employed to provide the one-trip unlatching action. Such a mechanism is not retrofitable on in-service flush-type door locks.
Prior to the conception of the present invention, applicant devised a flush-type door lock having a locking member rotatable by a key between positions for permitting or preventing unlocking operation of a handle. The lock included a single relatively stiff torsion spring which performed dual service in biasing two separate detent components of an automatic latching linkage. The linkage was intended to perform the functions of releasably retaining the locking member in an unlocked position following actuation by a key control, and of returning the locking member to its locked position following a single operation of the handle. The construction and arrangement of components utilized in this lock proposal was found to provide an unpractical device which was not reliable in its operation and which was difficult to assemble. Assembly of the components required that opposite ends of a relatively stiff, dual-function torsion coil spring be fitted into engagement with two separate detent components, both of which were movable relative to the lock body. Attempts to retrofit the proposed automatic locking linkage on existing in-service locks were found to be very difficult to carry out in the limited access space provided by many existing lock installations. A significant drawback of locks embodying the previously proposed construction was that opposite ends of the stiff, relatively heavily loaded, dual-purpose torsion spring tended to disengage themselves from one or both of the detent components. When the spring ends became disengaged, not only did the automatic locking feature cease to function, but also, in many instances, the lock was prevented from being locked even through manual efforts. While a few locks embodying this unsatisfactory proposal were sold more than one year prior to the filing of the present application, the majority of locks made embodying this proposal have been recalled and/or scrapped because the proposal embodied in such locks did not provide a commercially acceptable product.